Tracheal tubes (e.g. endotracheal and tracheostomy) are used by physicians for intubation into a patient's trachea for various purposes such as to enable the patient to breathe or to enable intermittent positive pressure ventilation of the respiratory tract. Various tracheal tube configurations are well known in the art, most of which include some form of expandable cuff for sealingly engaging the trachea wall. Typically, the cuff is inflated by room air using a syringe applied to a valve connected to the cuff filling pathway. The cuff is normally inflated to a pressure equal to or above the anticipated interpulmonary pressure to assure that the interpulmonary pressure does not compress the cuff and allow gas leakage out of the trachea. While inadequate pressure to seal the cuff against the trachea wall allows leakage of positive pressure gases, it has been recognized that excessive cuff pressure applied over extended periods may cause damage to the mucosa of the upper trachea; e.g. U.S. Pat. No. 3,640,282; "An Engineering Analysis of Intratracheal Tube Cuffs" by G. E. McGinnis et al, Anesthesia and Analgesia, July-August 1971; "The Endotracheal Cuff: A Comparative Study" by P. B. Dobrin et al, Anesthesia and Analgesia, May-June 1974.
Applicant's parent application discloses an expandable cuff system useful with tracheal tubes for effecting a seal against the trachea wall. The cuff system is comprised of a liquid reservoir formed by a readily deformable non-elastic wall coupled by a flexible filler pipe to an expandable cuff formed by flaccid readily deformable, non-distensible material. In use, after intubation of the tracheal tube into a patient's trachea, a valve in the filler pipe is opened and the reservoir is elevated above the trachea to cause the liquid to flow via gravity from the reservoir into the cuff thereby expanding the cuff wall against the trachea wall. After the cuff wall seals against the trachea wall, the reservoir is lowered to a level just above the cuff, thereby reducing the hydrostatic head and the pressure exerted by the cuff against the trachea wall. The valve in the filler pipe is then closed to maintain this low sealing pressure. To enable the user to conveniently handle the reservoir without applying pressure to the liquid therein, the reservoir is mounted within a vented rigid housing. A similar structure is disclosed in U.S. Pat. No. 3,766,927 issued to Richard R. Jackson.
Other expandable devices intended for insertion into the human body for purposes of sealing and/or restraining are disclosed in the following U.S. Pat. Nos. 3,087,492; 3,275,001; 3,394,705; 3,401,698; 3,640,282; 3,642,004; 3,625,793; 2,912,981; 3,045,677; 3,528,869; 2,919,697; 3,292,627; 2,896,629; 2,927,584; 3,409,016.